This invention concerns press mounted cams, which are mechanisms installed in forming presses to produce a feature on a workpiece being formed within the press by die having an upper part installed on an upper platen of the press and a lower die part installed on a lower press platen. The cam is used to form a punched or tapped hole where the feature is located such that it must be formed by tool motion along a direction at a working angle across the direction of press movement. The press mounted cams are used to produce such crossing tool motion.
These cams are comprised of a “slide”, carrying the tool, a “body” or “adapter” affixed to one of the die parts or press platens on which the slide is slidably mounted, and a separate “driver” mounted on the other of the die parts or press platen. The driver engages the slide and drives the same by engagement of cam surfaces when the press is operated.
In an “aerial” cam shown in FIG. 1, a slide 12 is suspended on a body or adapter 10 either directly mounted to the upper platen 2 or more typically to an upper part 6 of a forming die. A driver 14 is likewise either directly mounted to the lower platen 4 or more typically to a lower part 8 of a forming die and has fixed inclined cam surfaces 16 extending parallel to the working angle, typically defined by wear plates affixed to parallel faces on the driver 14 and slide 12.
As the upper platen 2 descends, a resulting cam action causes the slide 12 to be advanced along the working angle against the resistance of one or more springs 15, with tooling T projecting from the slide 12 driven in that direction. The horizontal component of the motion requires that the working slide 12 also move laterally on the adapter 10. Engaged horizontal bearing surfaces 18, 19 are provided on the top of the slide 12 and the bottom of the adapter 10 respectively for this purpose. In other configurations, an angled surface may be on the adapter, and a horizontal surface on the driver as in the embodiment seen in FIG. 12.
In a “die mounted” cam (shown in FIG. 2) the slide 12 and adapter 10 are both mounted to the lower platen 4 (or die part 8) which does not move, but rather the driver 14 is mounted to the moving upper platen 2 (or die part 6) and descends with the press upper platen 2 to engage the slide 12.
The die mounted cam thus does not result in vertical movement of the relatively heavy slide 12 with the upper platen 2, as occurs in an aerial cams. This vertical movement of the slide can cause problems as described below, but aerial cams are often used nonetheless since they create a clearance space to allow transfer of the workpieces into and out of the die and press.
In either cam mount design, in order to accurately locate the tooling T with respect to the workpiece W, the slide 12 must be accurately located laterally when being driven, and to achieve this, the practice heretofore has been to form the lower cam surfaces 16A in a V-shape so as to provide a lateral location of the slide on the driver as well as a camming surface as the slide 12 engages the driver 14 as seen in FIGS. 3 and 4.
Additional flat surfaces 16B are sometimes required for larger sized cams to provide adequate area to distribute the stresses imposed on the slider 12 by the press. Precision machining of the V-shaped surfaces is difficult and adds substantially to the cost of making the slide 12 and driver 14.
The slide 12 is suspended on the adapter 10 by means of side plates 20 engaged with hook over plates 22 attached to the sides of the slide 12. The slide 12 is guided along the plates 20, 22 when being advanced by the camming action on the slide 12 caused by the descent of the press upper platen.
The plates 22 are confined between side walls 24 to be laterally guided. A vertical hooked bar 26 is mounted on each side to reinforce the fixing of the plates 20.
Particularly in larger sizes, the need to machine features on the adapter 10 and slide 12 at locations on the outside of these components requires the use of large size machining centers, adding to substantially to the manufacturing costs.
In aerial cams, due to the large mass of the slider 12, an auxiliary roller cam 28 is provided to initiate and assist cammed lateral slide motion by engagement with a machined slot 30 on the driver 14, just prior to engagement of the cam surfaces. This helps to assist in redirection of the motion of slide 12 laterally to reduce peak stresses and consequent noise, shock, and wear of the cam surfaces. However, the roller cam 28 also adds substantially to the cost of such aerial cams.
A positive retraction auxiliary cam comprised of cam bars 32 and 34 is also provided to insure return movement of the slide 14 if return springs 38 in pockets 36 should fail due to excessive shock loading or are unable to withdraw the tool for some other reason such as a severely jammed tool.
The retraction cam bars 32, 34 are located at the outboard ends of the slide 12 and driver 14 and thus are difficult to machine especially in the larger cam sizes as described above. Also, the area of engagement therebetween is limited to the stroke of the slide 10, and the bars 32, 34 are subject to failure since a large force may be necessary to retract the slide 12 if a tool is severely hung up.
It is an object of the present invention to provide aerial cams which impose less shock on the mating components and to eliminate the need for auxiliary roller cams.
It is a further object to eliminate difficult to machine retention and locating features in both aerial and die mounted cams.
It is a further object to provide a more robust and durable positive retraction mechanism for both aerial and die mount cams.